African Female Breast Cancer Epidemiology (AFBRECANE) Study Project summary Breast cancer is the commonest cancer in women globally and it is increasingly overtaking cervical cancer as the commonest female cancer in low and middle income countries (LMIC). The incidence of breast cancer Nigeria was 54.3 per 100,000 per year (24,750 new cases per year) in 2014 representing a rise from 20 per 100,000 in the 1970s (3,000 new cases per year). It is now a major cancer burden in Nigerian women. There are controversies about the epidemiology and molecular subtypes of breast cancer in African women including limited knowledge about the incidence of breast cancer and determinants of this incidence such as the role of different risk factors; incidence and prevalence of molecular subtypes of breast cancer and the contributions of indigenous African diets to breast cancer incidence. In the absence of prospective cohort studies, we engage innovative research design and analytic techniques to use data from population based cancer registries (PBCR) to study the epidemiological factors associated with incident breast cancer and molecular subtypes. There has also never been a genome wide association study (GWAS) of breast cancer in general and of molecular subtypes of breast cancer in indigenous African women. While many researchers suggest that African diets are associated with reduced risks of breast cancer, there have been very few systematic studies. We use the nutrition epidemiology tools that we previously developed and validated to study dietary intakes and breast cancer risk in African women. We focus in particular on the role of vitamin D and explore potential associations with breast cancer using nutrition epidemiology and genomics epidemiology tools.